CN110627949A

CN110627949A - Hybrid latex emulsions and coating compositions formed from hybrid latex emulsions

Info

Publication number: CN110627949A
Application number: CN201910973317.6A
Authority: CN
Inventors: C·李; T·I·迈莫尔; D·斯卡武佐; D·博德
Original assignee: Akzo Nobel Coatings International BV
Current assignee: Akzo Nobel Coatings International BV
Priority date: 2013-03-14
Filing date: 2014-03-11
Publication date: 2019-12-31
Also published as: AU2014230938A1; ZA201506222B; MY183569A; AU2014230938B2; CN105189662A; KR102325152B1; MX375944B; PL2970682T5; US10865324B2; MX2015011950A; EP2970682B2; BR112015021340A2; CA2904159C; RU2660133C2; EP2970682B1; RU2015142519A; KR20150128758A; BR112015021340B1; EP2970682A1; HK1218132A1

Abstract

Hybrid latex emulsions are disclosed that can be used to form coating compositions having good blush resistance, abrasion resistance, blistering resistance, hardness, and scratch resistance. In some embodiments, the coating compositions are used to coat substrates such as cans and packaging materials used to store food and beverages. The hybrid latex emulsion of the present invention can be prepared by mixing an ethylenically unsaturated monomer component and a stabilizer in a carrier to form a monomer emulsion and reacting the monomer emulsion with an initiator to form the hybrid latex emulsion. The ethylenically unsaturated monomer component can include an organosilane compound, which can include a reactive organic group and a hydrolyzable inorganic alkoxysilane.

Description

Hybrid latex emulsions and coating compositions formed from hybrid latex emulsions

This application is a divisional application of patent application No. 201480014510.2, filed as 2014 3/11 entitled "hybrid latex emulsion and coating composition formed from hybrid latex emulsion".

Background

1. Field of the invention

The present invention relates to hybrid latex emulsions, coating compositions formed from the hybrid latex emulsions, methods of coating substrates with the coating compositions, and substrates coated with the coating compositions.

2. Description of the related Art

Coating compositions formed from epoxy resins have been used to coat packaging and containers for food and beverages. While the importance of scientific evidence as explained by the major global food safety agencies in the united states, canada, europe, and japan indicates that the bisphenol a content of current commercial epoxy-based coatings exposed to consumers is safe, some consumers and brand owners continue to express concern and need a coating that does not contain bisphenol a or any other endocrine disrupters.

Commonly owned WO 2010/97353 describes the preparation of latex emulsions for use in coating compositions that can be used for package coating of beverages in-spray applications. Commonly owned patent publication WO 2012/089747 describes the preparation of core-shell latex emulsions for beverage cap applications. Such latex emulsions have not achieved the performance of epoxy-based coatings and have not been successfully used on an industrial basis as food and beverage coating compositions.

It is desirable to produce coating compositions that are free or substantially free of bisphenol a. There is also a need to produce coating compositions that are free or substantially free of phenolic resin.

Summary of The Invention

The present invention provides an epoxy resin substitute that still allows for formaldehyde and phenol free or substantially phenol free curing, blush resistance, retortability and can withstand difficult to hold beverages. The coating compositions of the present invention can be prepared in a simple process, requiring no multiple polymers or multiple processing stages to achieve the desired effect.

The hybrid latex emulsion of the present invention can be prepared by a sol-gel process to introduce self-crosslinking functional groups into the hybrid latex emulsion particles to help increase the gel content and blush resistance of the hybrid latex emulsion particles. These hybrid latex emulsions can be used to prepare coating compositions that are free or substantially free of phenolic resins, which are particularly suitable as packaging coatings for food and beverage packaging and containers, including beer and beverage inside/outside easy-open lids. Easy-open lids for beer and beverage containers are typically manufactured by first coating a flat sheet of a metal substrate, heating the coated substrate and then stamping or forming the coated substrate into the desired shape. Coatings for beer and beverage can ends can be applied on high speed coil coating lines at film weights of about 1-15 mg/sq inch. High speed coil coating lines require a coating that dries and cures in a few seconds because it is heated very quickly to a peak metal temperature that can be about 200 and 300 ℃.

Organosilane compounds, such as alkoxysilanes, can be incorporated into the hybrid latex emulsion of the present invention to aid in the formation of self-crosslinkable films. As a result, organosilane-acrylate copolymer hybrid latex emulsions can be prepared having specific properties designed to take advantage of the combination of water repellency, non-staining, and thermal stability of organosilane compounds, as well as the mechanical strength and cohesion of acrylic matrices.

While previous literature suggests that organosilane compounds improve adhesion, the inventors of the present invention have found that organosilane compounds also improve key quality performance parameters of food and beverage packaging and containers, particularly coatings for beer and beverage lids. In commonly owned WO 2010/97353, it is difficult to achieve sterilization resistance using high film thicknesses. The incorporation of the organosilane compound in the present invention allows the coating composition to have a higher gel content, which allows for higher film weights, while still achieving a non-whitish film after sterilization. The thicker films of the present invention meet the global requirements for beer and beverage cap applications.

The present invention includes a method of preparing a stable hybrid organosilane-acrylate copolymer latex emulsion (e.g., hybrid silicone-acrylate copolymer latex emulsion) by emulsion polymerization or microemulsion polymerization. In some embodiments of the invention, a hybrid latex emulsion is prepared by a method comprising the steps of mixing an ethylenically unsaturated monomer component and a stabilizer in a carrier to form a monomer emulsion and reacting the monomer emulsion with an initiator to form the hybrid latex emulsion, wherein the ethylenically unsaturated monomer component comprises an organosilane compound and at least one ethylenically unsaturated monomer that is not an organosilane compound. The mixing of the ethylenically unsaturated monomer component and the stabilizer in the carrier may be carried out using a high shear Ross mixer at moderate speed for about 10 minutes, followed by high speed (>10,000rpm) for an additional about 10 minutes to obtain stable particles. The mixture may be pumped into a reactor with an initiator solution to form a hybrid latex emulsion.

In some embodiments of the invention, the hybrid latex emulsion is used as or to form a coating composition for food and beverage packaging and containers per se. In some embodiments of the invention, the hybrid latex emulsion may be blended with an organosilane compound, such as a colloidal silica dispersion, to improve blush resistance, abrasion resistance, blistering resistance, hardness, and scratch resistance. In addition, the hybrid latex emulsions and coating compositions of the present invention can also be prepared without phenolic compounds.

The invention also includes a method of coating a substrate with the coating composition having the mixed latex emulsion and a substrate coated with the coating composition.

Detailed Description

The present invention includes substrates at least partially coated with the coating compositions of the present invention and methods of coating a substrate. The term "substrate" as used herein includes, but is not limited to, cans, metal (e.g., aluminum) cans, beer and beverage easy-open lids, packages, containers, reservoirs, or any portion thereof for holding, abutting, or contacting any type of food or beverage. Also, the terms "substrate," "food can," "food container," and the like include, as non-limiting examples, "can lids," which can be stamped and formed from can lid stock and used in beverage packaging.

The present invention includes a method of preparing a hybrid latex emulsion by mixing an ethylenically unsaturated monomer component and a stabilizer in a carrier to form a monomer emulsion and reacting the monomer emulsion with an initiator to form the hybrid latex emulsion, wherein the ethylenically unsaturated monomer component includes an organosilane compound and at least one ethylenically unsaturated monomer that is not an organosilane compound. In some embodiments, the organosilane compound is present in the hybrid latex emulsion in an amount of about 0.1 to 30 weight percent of the total polymer solids. In some embodiments, the stabilizer is present in the hybrid latex emulsion in an amount of about 0.1 to 5.0 weight percent of the total polymer solids.

In some embodiments of the invention, the hybrid latex emulsion is prepared by microemulsion polymerization. In this process, the ethylenically unsaturated monomer component, stabilizer and carrier can be mixed using a high shear Ross mixer at moderate speed for 10 minutes and then at high speed (>10,000rpm) for an additional 10 minutes to obtain stable particles. The mixture may be pumped into a reactor with an initiator solution to form a hybrid latex emulsion.

In some embodiments of the invention, a hybrid core-shell latex emulsion can be prepared from an ethylenically unsaturated monomer component, a stabilizer comprising a strong acid, and an initiator. The ethylenically unsaturated monomer component can include an organosilane compound present in the core or shell of the hybrid core-shell latex emulsion. The hybrid core-shell latex emulsions of the present invention may comprise a homogeneous latex particle structure and/or a heterogeneous latex particle structure. The core-shell latex particle structure can be controlled by the polymerization process. The particle structure is typically prepared by a series of sequential emulsion polymerization sequences using different monomer types, wherein the second stage monomer is polymerized in the presence of the seed latex particle. In some embodiments, the hybrid latex emulsion is reacted with a neutralizing agent to form a coating composition.

The hybrid latex emulsion of the invention can be prepared using an ethylenically unsaturated monomer component having an organosilane compound and at least one ethylenically unsaturated monomer that is not an organosilane compound. The organosilane compound may include, but is not limited to, 3-trimethoxysilylpropyl Methacrylate (MPS), 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, Vinyltriethoxysilane (VTES), tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, colloidal silicon dioxide, inorganic silica particles, and the like, or combinations thereof.

When VTES or MPS is present, for example, in the mixture of ethylenically unsaturated monomer components, three sets of chemical reactions (depending on reaction conditions such as pH, temperature and monomer composition) may occur simultaneously. First, organosilane silane monomers (such as MPS) may be incorporated into the polymer chain by free radical copolymerization as shown in scheme 1 below. In scheme 1, R₁May be hydrogen or methyl, R₂、R₃And R₄Each of which may be methyl, ethyl, isopropoxy or phenyl, R₅And may be hydrogen, methyl, ethyl, butyl or 2-ethylhexyl, such as 2-hydroxyethyl or hydroxypropyl. The polymerization reaction may include both a radical polymerization reaction of the acrylate monomer and a hydrolytic condensation reaction of the organosilane compound. Secondly, as illustrated in scheme 2, the trimethoxysilyl and hydroxyl groups in the copolymer may undergo hydrolysis and polycondensation reactions, resulting inThe hybrid latex emulsion is crosslinked. In scheme 2, the amount of organosilane compound incorporated into the copolymer chain may depend on the particular surfactant, ethylenically unsaturated monomer component mixture, temperature, and pH. Both acidic and basic catalysts confirm the hydrolysis of the alkoxysilanes. Good pH control is required to minimize premature crosslinking during polymerization. For most systems, a minimum rate of hydrolysis may occur at neutral pH. If a more sterically hindered alkoxysilane, for example alkyltriisopropoxysilane, is used instead of alkyltrimethoxysilane, less premature crosslinking can result than if methacryloxypropyltriisopropoxysilane were used.

Scheme 1-copolymerization reaction scheme

Scheme 2-reaction scheme for hydrolysis/condensation of hybrid latex

In some embodiments, the hybrid latex emulsion may be neutralized. The neutralizing agent may include, but is not limited to, ammonia, tertiary amines such as dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, tributylamine, or combinations thereof as non-limiting examples. By way of non-limiting example, the neutralizing agent may be used in an amount up to about 100% based on the amount of acid to be neutralized in the system.

At higher pH, silanol groups from the organosilane compound and hydroxyl groups from the acrylate compound of the ethylenically unsaturated monomer component present in the latex polymer chain can undergo condensation reactions. The condensation reaction rate can be increased when the pH and/or temperature is increased, resulting in a highly crosslinked interpenetrating network as shown in scheme 3. Inorganic silica particles from the organosilane compound can be dispersed in the resulting organic polymer to form hybrid latex emulsion particles. The formation of a silica network can improve the thermal stability, mechanical strength and blush resistance of the hybrid latex emulsion particles in the coated film.

Scheme 3 hybrid latex interpenetrating network particles

In some embodiments, the organosilane compound may be used as a coupling agent to link the inorganic phase of the hybrid latex emulsion to the organic phase of the hybrid latex emulsion. Inorganic silica compounds such as Tetraethoxysilane (TEOS), Tetramethoxysilane (TMOS), methyltrimethoxysilane, phenyltriethoxysilane, and the like, or mixtures thereof, may be incorporated into the latex emulsion particles. The vinyl group present in the organosilane compound can react with various ethylenically unsaturated monomers, while trimethoxy group present in the organosilane compound can undergo hydrolysis to form silanol compounds. The silanol compound can react with the silanol groups of the organosilane compound to form an inorganic polymer. In some embodiments, colloidal silica dispersions such as, but not limited to, colloidal silica dispersions may be usedCC301 is blended with the hybrid latex emulsion to increase the hardness, abrasion resistance, and scratch resistance of the hybrid latex emulsion.

The organosilane compound can be polymerized with the ethylenically unsaturated component to form an interpenetrating network, such as the interpenetrating network shown in scheme 4. In the interpenetrating network, condensation reactions of silanol groups in the organosilane compound form Si-O-Si bridges that crosslink the polymer chains. The interpenetrating network is defined as conventional TⁿWherein T represents a trifunctional unit and n is the number of bridging O atoms surrounding the silicon atom. In scheme 4, T^oCan be trisilanol or trialkoxysilane. T is³The network with the largest cross-linking in scheme 4. The interpenetrating network can improve the blush resistance and distillation resistance of the hybrid latex emulsion.

Scheme 4 interpenetrating networks

In some embodiments, the organosilane compound may be used as a coupling agent by including one or more reactive organic groups and one or more hydrolyzable inorganic groups. The reactive organic groups may include vinyl groups, epoxy groups, amino groups, and the like, or mixtures thereof. The hydrolyzable inorganic group may include an alkoxysilyl group. It is contemplated that the dual nature of the organosilane compound allows the organosilane compound to react with both inorganic and organic polymers as shown in scheme 5.

Scheme 5 reaction of acidic organic Polymer with 3-glycidoxypropyltrialkoxysilane (R may be methyl or ethyl)

The hybrid latex emulsions of the present invention may have a relatively uniform latex particle structure and/or a non-uniform latex particle structure. The mixed latex particle structure can be controlled by polymerization processes including, as non-limiting examples, multi-stage polymerization processes. The particle structure is typically prepared by a series of sequential emulsion polymerization sequences using different monomer types, wherein the second stage monomer is polymerized in the presence of the seed latex particle.

The coating compositions of the present invention are suitable for packaging coating applications, such as beverage cap applications having a cure time of less than about 15 seconds. In some embodiments, the coating composition has a gel content of greater than about 50 or greater than about 90.

The hybrid latex particle structure of the present invention allows for the incorporation of lower levels of acid monomer, thereby contributing to better blush resistance and acceptable adhesion to substrates. Lower levels of acid monomer can be used in the emulsion polymerization, such as from about 0.5 to 10% or from about 1.2 to 5% based on the total solids content of the ethylenically unsaturated monomer component mixture.

In some embodiments, the hybrid latex emulsions used in the present invention may be prepared by techniques known in the art such as, but not limited to, suspension polymerization, interfacial polymerization, and emulsion polymerization. Emulsion polymerization techniques for preparing latex emulsions from ethylenically unsaturated monomer components are well known in the polymer art and any conventional latex emulsion technique may be used, such as single and multi-step batch and continuous processes as non-limiting examples. In some embodiments, the ethylenically unsaturated monomer component (which may include and/or act as a crosslinking agent) is prepared and added to the polymerization vessel at various stages. The order of addition of the monomers (e.g., hydroxyl, organosilane, and acid monomers) can be from the most hydrophobic to the most hydrophilic, which helps to improve distillation resistance, stabilize the latex particles, and provide good wetting and adhesion on the coated substrate. The ethylenically unsaturated monomer component (e.g., glycidyl methacrylate, glycerol dimethacrylate, 1, 4-butanediol dimethacrylate, or combinations thereof) may include and/or act as a crosslinker to enhance the mechanical properties and abrasion resistance of the film. The ethylenically unsaturated monomer component can be varied during the polymerization process, such as by varying the composition of the ethylenically unsaturated monomer component fed to the vessel, as a non-limiting example. Both single stage and multistage polymerization techniques can be used. In some embodiments, the hybrid latex emulsion is prepared using a seed monomer emulsion to control the number and size of particles produced by emulsion polymerization. The particle size of the hybrid latex emulsion polymer particles is controlled in some embodiments by adjusting the initial surfactant charge.

There are at least several different ways to crosslink the hybrid latex emulsion to increase molecular weight. In one embodiment, the hybrid latex emulsion may be crosslinked by at least one ethylenically unsaturated monomer component such as tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerol di (meth) acrylate, or combinations thereof. In another embodiment, if the hybrid latex emulsion has a functional group, such as methacrylic acid, the hybrid latex emulsion can be crosslinked by a glycidyl group, such as, but not limited to, glycidyl methacrylate. In a third embodiment, if the hybrid latex emulsion has a hydroxy-functional monomer, such as, but not limited to, hydroxypropyl methacrylate, the hybrid latex emulsion can be crosslinked with a phenolic resin to achieve suitable physical properties of the hybrid latex emulsion on a substrate.

Suitable crosslinking agents may include, but are not limited to, urea-formaldehyde resins, phenol-formaldehyde resins, benzoguanamine-formaldehyde resins, phenolic resins, and combinations thereof. In some embodiments of the invention, the ethylenically unsaturated monomer component may include and/or act as a crosslinking agent. In addition, the crosslinking agent may be added as a separate component from the ethylenically unsaturated monomer component. In some embodiments, the amount of crosslinking agent is about 0.1 to 30 weight percent based on total polymer solids in the hybrid latex emulsion. The crosslinker can help improve chemical resistance and/or water blush resistance. However, if the amount of the crosslinking agent is too high, the film may lose flexibility.

The hybrid latex emulsion particle structure can be controlled by the polymerization process. Hybrid latex emulsion particles can be prepared by a series of sequential emulsion polymerization sequences using different monomer types, wherein the second stage (third stage, etc.) monomers are polymerized in the presence of the seed latex particles. These seed particles may be prepared in a separate step or formed in situ during the emulsion polymerization.

In various embodiments of the present invention, the ethylenically unsaturated monomer component can be comprised of a single monomer or a mixture of monomers. When the emulsion is polymerized using at least one different ethylenically unsaturated monomer component to prepare a hybrid latex emulsion, the at least one different ethylenically unsaturated monomer component can be added to the monomer mixture. In some embodiments, the ethylenically unsaturated monomer component may include and/or act as a crosslinking agent. In some embodiments, the ethylenically unsaturated monomer component and/or the different ethylenically unsaturated monomer component can be present in an amount up to about 60% based on the total solids content of the mixture of ethylenically unsaturated monomer components. The ethylenically unsaturated monomer component and the different ethylenically unsaturated monomer component may include, but are not limited to, organosilane compounds having one or more reactive organic groups and one or more hydrolyzable inorganic groups, one or more vinyl monomers, acrylic monomers, allylic monomers, acrylamide monomers, vinyl esters including, but not limited to, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl isopropyl acetate, and similar vinyl esters, vinyl halides including, but not limited to, vinyl chloride, vinyl fluoride, and vinylidene chloride, vinyl aromatics including, but not limited to, styrene, methyl styrene, and similar lower alkyl styrenes, chlorostyrene, vinyl toluene, vinyl naphthalene, including, but not limited to, alpha-olefins such as, by way of non-limiting example, ethylene, propylene, and the like, Vinyl aliphatic hydrocarbon monomers of isobutylene and cyclohexene, as well as conjugated dienes such as, by way of non-limiting example, 1, 3-butadiene, methyl-2-butadiene, 1, 3-piperylene, 2, 3-dimethylbutadiene, isoprene, cyclohexane, cyclopentadiene, dicyclopentadiene, and combinations thereof. The vinyl alkyl ether may include, but is not limited to, methyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, and combinations thereof. Acrylic monomers can include, but are not limited to, monomers such as, by way of non-limiting example, lower alkyl esters of acrylic or methacrylic acid having alkyl ester moieties other than methyl or ethyl containing from about 3 to 10 carbon atoms, as well as aromatic derivatives of acrylic and methacrylic acid and combinations thereof. Acrylic monomers may include, as non-limiting examples, butyl acrylate and methacrylate, propyl acrylate and methacrylate, 2-ethylhexyl acrylate and methacrylate, cyclohexyl acrylate and methacrylate, decyl acrylate and methacrylate, isodecyl acrylate and methacrylate, benzyl acrylate and methacrylate, various glycidyl ethers reactive with acrylic and methacrylic acid, hydroxyalkyl acrylates and methacrylates such as, but not limited to, hydroxyethyl acrylate and methacrylate and hydroxypropyl acrylate and methacrylate, as well as amino acrylates and amino methacrylates and combinations thereof.

In some embodiments, the ethylenically unsaturated monomer component and/or the different ethylenically unsaturated monomer component includes at least one multi-ethylenically unsaturated monomer component effective to increase molecular weight and aid in crosslinking the polymer. Non-limiting examples of multi-ethylenically unsaturated monomer components include allyl (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 3-butanediol (meth) acrylate, polyalkylene glycol di (meth) acrylate, diallyl phthalate, trimethylolpropane tri (meth) acrylate, divinylbenzene, divinyltoluene, trivinylbenzene, divinylnaphthalene, and combinations thereof. In some embodiments, the multi-ethylenically unsaturated monomer component is present in an amount of about 0.1 to 5% of the total solids content of the mixture of ethylenically unsaturated monomer components.

In some embodiments of the invention, the ethylenically unsaturated monomer component and/or the different ethylenically unsaturated monomer component is mixed with a stabilizer in a carrier to form a monomer emulsion. Optionally, a base is present in the mixture. In some embodiments, the stabilizer is present in an amount of about 0.1 to 5.0 weight percent of the polymer solids.

The stabilizer may include a strong acid. Non-limiting examples of stabilizers include, but are not limited to, dodecylbenzene sulfonic acid, dinonylnaphthalene disulfonic acid, di (2-ethylhexyl) sulfosuccinic acid, and the like, including combinations thereof. In some embodiments, the strong acid is an acid having a dissociation constant (pKA) in aqueous solution of less than about 4. In some embodiments, the strong acid has a hydrophobe attached to the acid. In some embodiments, the strong acid has at least about 6 carbon atoms.

Non-limiting examples of bases include ammonia, dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, and combinations thereof. In some embodiments, the base is present in an amount of about 50 to 100 mol% relative to the stabilizer.

In some embodiments, the carrier includes, but is not limited to, water, a water-soluble co-solvent, or a combination thereof. In some embodiments, the carrier is present in an amount of about 30-70% by weight of the hybrid latex emulsion.

In some embodiments of the invention, the monomer emulsion and/or the hybrid latex emulsion is reacted with one or more initiators. The initiator may include, as a non-limiting example, an initiator that thermally decomposes at a polymerization temperature to generate radicals. Examples of initiators include, but are not limited to, both water soluble and water insoluble materials, and combinations thereof. Examples of free-radical generating initiators may include, as non-limiting examples, persulfates such as, but not limited to, ammonium persulfate or alkali metal (potassium, sodium, or lithium) persulfates, azo compounds such as, but not limited to, 2 '-azobisisobutyronitrile, 2' -azobis (2, 4-dimethylvaleronitrile), and 1-t-butyl azocyanocyclohexane, hydroperoxides such as, but not limited to, t-butyl hydroperoxide and cumene hydroperoxide, peroxides such as, but not limited to, benzoyl peroxide, octanoyl peroxide, di-t-butyl peroxide, ethyl 3,3 '-di (t-butylperoxy) butyrate, ethyl 3,3' -di (t-amylperoxy) butyrate, t-amyl peroxy-2-ethylhexanoate, and t-butyl peroxypivalate, peresters such as, but not limited to, t-butyl peracetate, t-butyl perphthalate, and t-butyl perbenzoate, percarbonates such as, but not limited to, bis (1-cyano-1-methylethyl) peroxycarbonate, perphosphate esters, and the like, and combinations thereof.

In some embodiments, the initiator is used alone or as an oxidizing component of a redox system that can include, but is not limited to, a reducing component such as, as non-limiting examples, ascorbic acid, maleic acid, glycolic acid, oxalic acid, lactic acid, thioglycolic acid, or alkali metal sulfites such as, but not limited to, bisulfites, dithionites, or metabisulfites such as, but not limited to, sodium bisulfite, potassium dithionite, and potassium metabisulfite, or sodium formaldehyde sulfoxylate and combinations thereof. The reducing component may be referred to as an accelerator or catalyst activator.

In some embodiments, the initiators and accelerators, which may be referred to as initiator systems, are used in proportions of about 0.001 to 5% based on the weight of the ethylenically unsaturated monomer component to be copolymerized. Promoters such as, but not limited to, chlorides and sulfates of cobalt, iron, nickel, or copper are optionally used in some embodiments in amounts of about 2 to 200 ppm. Non-limiting examples of redox catalyst systems include, but are not limited to, t-butyl hydroperoxide/sodium formaldehyde sulfoxylate/fe (ii) and ammonium persulfate/sodium bisulfite/sodium dithionite/fe (ii) and combinations thereof. In some embodiments, the polymerization temperature is from about room temperature to about 90 ℃ and this temperature can be optimized for the initiator system used as is conventional.

In some embodiments of the invention, aggregation of the polymer latex particles is limited by the introduction of a stabilizing surfactant during polymerization. By way of non-limiting example, the growing latex particles may be stabilized during emulsion polymerization by one or more surfactants such as, but not limited to, dodecylbenzene sulfonic acid, anionic or nonionic surfactants, or combinations thereof, as are well known in the polymerization art. Other types of stabilizers such as, but not limited to, protective colloids may be used in some embodiments. In general, conventional anionic surfactants with metals, nonionic surfactants containing polyethylene chains, and other protective colloids tend to impart water sensitivity to the resulting film. In some embodiments of the present invention, it is desirable to minimize or avoid the use of these conventional anionic and nonionic surfactants. In some embodiments, a stabilizing surfactant is used during seed polymerization.

Chain transfer agents are used in some embodiments of the invention to help control the molecular weight of the hybrid latex emulsion. Non-limiting examples of chain transfer agents may include mercaptans, polythiols, polyhalo compounds, alkyl mercaptans such as, but not limited to, ethyl mercaptan, n-propyl mercaptan, n-butyl mercaptan, isobutyl mercaptan, t-butyl mercaptan, n-pentyl mercaptan, isopentyl mercaptan, t-pentyl mercaptan, n-hexyl mercaptan, cyclohexyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, mercaptocarboxylic acids and esters thereof, such as, but not limited to, methyl mercaptopropionate and 3-mercaptopropionic acid, alcohols such as, but not limited to, isopropanol, isobutanol, lauryl alcohol and t-octanol, halogenated compounds such as, but not limited to, carbon tetrachloride, tetrachloroethylene, trichlorobromoethane, and combinations thereof. In some embodiments, up to about 10 weight percent chain transfer agent is used based on the weight of the ethylenically unsaturated monomer component mixture. In some embodiments the hybrid latex emulsion molecular weight can be controlled by controlling the ratio of initiator to ethylenically unsaturated monomer component.

In some embodiments, the initiator system and/or chain transfer agent are dissolved or dispersed in a separate fluid medium or the same fluid medium and then gradually added to the polymerization vessel. In some embodiments, the ethylenically unsaturated monomer component (neat or dissolved or dispersed in a fluid medium) is added simultaneously with the catalyst and/or chain transfer agent. The catalyst may be added to the polymerization mixture after the polymerization has been substantially completed to "chase" residual monomer, thereby polymerizing the residual monomer.

In some embodiments, an additional monomer mixture of an ethylenically unsaturated monomer component and a stabilizer is added to the monomer emulsion. Optionally, a base is present in the additional monomer mixture. In some embodiments, the additional monomer mixture may be added to the monomer emulsion before the initiator is added, after the initiator is added, or both before and after the initiator is added. The composition of the ethylenically unsaturated monomer component, stabilizer and base in the additional monomer mixture may be the same as or different from the composition of these components in the monomer emulsion.

In some embodiments of the present invention, the hybrid latex emulsion may be reacted with a neutralizing agent to form a coating composition. In some embodiments, the reaction is carried out in the presence of a solvent, with or without a phenolic crosslinking agent such as, but not limited to, MC-16 by Sakuranomiya chemical Company, EP-560 by Cytec, PH2028, PH2013/65B, PR899/60MPC, PF6535LB by Hexion, SFC112/65 by SI Group, 7700LB by Ruters, or combinations thereof. Solvents may include, but are not limited to, xylene, benzene, ethylbenzene, toluene, alkoxy alkanols, methanol, ethanol, propanol, butanol, alkyl ethers of ethylene, alkyl ethers of propylene glycol, ethylene glycol monobutyl ether, ethylene glycol ethyl ether, diethylene glycol monobutyl ether, ketones, aromatic solvents, ester solvents, hydroxy-functional solvents, and combinations thereof. The amount of solvent in the coating composition may be up to about 90% by weight of the polymer solids or about 20-45% by weight of the liquid coating composition. If water is present, the amount of water in the coating composition may be about 20% to 50%.

In some embodiments, neutralizing agents include, but are not limited to, ammonia, tertiary amines such as dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, tributylamine, or combinations thereof, as non-limiting examples. By way of non-limiting example, the neutralizing agent may be used in an amount up to about 100% based on the amount of acid to be neutralized in the system.

The glass transition temperature (Tg) of the composition may depend on the total monomer composition and may contribute to blush resistance, performance lubricant (lube bloom) and abrasion resistance. By way of non-limiting example, if the polymer has an increased amount of methacrylic acid, the polymer may have a higher Tg. In some embodiments of the invention, the Tg is from about 5 to about 50 ℃. If the Tg is too low, the film may be too soft and may have insufficient abrasion resistance. If the Tg is too high, the film may wrinkle and may not have sufficient flexibility, which may reduce film performance. The curing temperature may be about 200-300 deg.c.

The hybrid latex emulsions and coating compositions of the present invention may include conventional additives known to those skilled in the art, such as, but not limited to, additives to control foam, reduce equilibrium and dynamic surface tension, or control rheology and surface lubricity. The amount may vary in any manner known to those skilled in the art depending on the desired coating application and properties.

In some embodiments, one or more coating compositions of the present invention may be applied to a substrate such as, by way of non-limiting example, cans, metal cans, beer and beverage easy-open lids, packages, containers, reservoirs, can lids, or any portion thereof, for holding or contacting any type of food or beverage. In some embodiments, one or more coating compositions are applied in addition to the coating compositions of the present invention, such as by way of non-limiting example, a primer coat may be applied between the substrate and the coating composition of the present invention.

The coating composition may be applied to the substrate in any manner known to those skilled in the art. In some embodiments, the coating composition is sprayed onto the substrate. When sprayed, the coating composition may contain, as a non-limiting example, about 10-30% by weight polymer solids, relative to about 70-90% water, including other volatiles such as, but not limited to, minimal amounts of solvents, if desired. For some applications, typically those other than spraying, the aqueous polymer dispersion may contain, as a non-limiting example, about 20-60% by weight polymer solids. Organic solvents may be used in some embodiments to facilitate spraying or other application methods and such solvents may include, but are not limited to, n-butanol, 2-butoxyethanol-1, xylene, toluene, and mixtures thereof. In some embodiments, n-butanol is used in combination with 2-butoxyethanol-1. In some embodiments the coating compositions of the present invention may be pigmented and/or opacified with known pigments and opacifiers. For many applications, including food applications as non-limiting examples, the pigment may be titanium dioxide.

The resulting aqueous coating composition may be applied in some embodiments by conventional methods known in the coatings industry. Thus, as non-limiting examples, spray, roll, dip and flow application methods can be used for both clear and colored films. In some embodiments, after application to the substrate, the coating may be thermally cured at a temperature of about 215-250 ℃ or at a higher temperature for a time sufficient to effect complete curing and volatilization of any temporary components therein.

For substrates intended as beverage containers, the coating composition may be applied in some embodiments at a rate of about 0.5 to 15mg of polymer coating per square inch of exposed substrate surface. In some embodiments, the water-dispersible coating composition may be applied at a thickness of about 1 to 25 microns.

The present invention provides ease of manufacture compared to conventional epoxy-acrylic commercial materials, since a single polymer can be used in the emulsion polymerization process. It is surprising that the desired properties can be achieved by a sol-gel crosslinking reaction. A unique aspect of the present invention is that an organosilane compound (such as MPS or 3-glycidoxypropyltrimethoxysilane) can be used in the hybrid latex emulsion to help obtain hybrid latex emulsions and coating compositions with acceptable blush resistance, abrasion resistance, blistering resistance, hardness, and scratch resistance. Additional phenolic resin or crosslinking agent may be blended into the hybrid latex emulsion to enhance film properties. The coating composition of the present invention can be applied to a panel and can be applied during the manufacture of a beverage easy-open end for packaging coating applications.

For substrates intended as beverage easy-open ends, the coating is applied in some embodiments at a rate of about 1.5 to 15 milligrams of polymer coating per square inch of exposed substrate surface. Conventional packaging coating compositions are applied to metals at about 232-247 ℃. Some coating compositions of the present invention achieve good results at about 230 ℃ or less, such as about 210 ℃ or less. This reduced temperature provides energy savings for the coater and may allow the use of different alloys, such as tin-plated steel for easy-open ends. This also allows the lid to be recycled with the can.

Examples

The invention is further illustrated with reference to the following non-limiting examples. It is to be understood that variations and modifications in those embodiments may occur to those skilled in the art without departing from the spirit and scope of the invention.

The gel content was measured as follows:

1. the sample was placed in a PTFE 10cc centrifuge tube and 10cc of unstabilized THF was added. The tube and sample weights are known.

2. The sample solution was dissolved overnight and ultracentrifuged at 20,000rpm for 5 hours the following day using a Beckman-Coulter (Avanti J-E).

3. The tubes were removed as soon as possible after the ultracentrifugation step was completed and the gel "type" was observed. The gel was mobile and difficult to see clearly (not fully granulated). Because the material is not fully or partially granulated, it is recognized that there is a balance between taking as much supernatant as possible and not taking the gel. Approximately 8.5-9.5cc of supernatant was removed, leaving some supernatant containing soluble material.

4. The "removed" supernatant was filtered through a 0.45 μm syringe filter prior to GPC analysis.

5. The PTFE tube with insoluble material was dried in a fume hood overnight and then heated under vacuum at 62 ℃ for 4-5 hours the next day to drive off any residual THF.

6. The dried insolubles and tube weight were read and the tube weight was reduced.

% gel content calculation：

(insoluble matter weight (g) × 100)/(sample weight (g) × NV)% gel content

Blush resistance is a measure of the ability of a coating to resist attack by various solutions. Blush is usually measured by the amount of water absorbed into the coated film. When the film absorbs water, it generally becomes cloudy or appears white. The coating compositions were evaluated by distillation with deionized water (immersion in 250F water for 90 minutes). The retort blush was visually measured on a scale of 0-5. A whitish 0 means no whitish. A whitish 5 means that the film is completely white.

Beaded Ericksen cup fabrication (bead Ericksen cup fabrication) measures the ability of a coated substrate to retain its integrity while simulating the forming process used to produce beverage can lids. It is a measure of the presence of cracks or breaks in the bead. A1X 1 inch immersion cup is manufactured by Ericksen cup.

Adhesion tests were performed on beaded erichsons to assess whether the coating adhered to the cup. Adhesion testing was performed according to ASTM D3359-test method B using SCOTCH 610 tape available from 3M Company, Saint Paul, Minnesota. Adhesion is generally evaluated on a scale of 0 to 5, where a score of "0" indicates no adhesion failure and a score of "5" indicates complete removal of the film from the substrate.

Foaming was measured by MEIJI Techno Microcoseps citation ASTM D714. Foaming is evaluated in this application by none, few and dense.

Example 1 comparison

The present invention can use a sol-gel process to prepare a highly mixed organic-inorganic hybrid latex emulsion for can coating compositions. The silica particles are effective to improve the blush resistance and abrasion resistance of the coating composition. Example 1 is a comparative example because it does not include methacrylic silane monomer.

The following acrylate latices were prepared with 6% by weight (based on the total weight of the monomers) of 1, 3-Glycerol Dimethacrylate (GDMA) without the use of the organosilane compound 3-Methacryloxypropyltrimethoxysilane (MPS):

group a and group B were added to the flask and heated to 77 ℃ under nitrogen sparge. The stirring was turned on. The nitrogen sparge was changed to a blanket when the temperature reached 77 ℃.

A pre-emulsion is used in the polymerization to aid in the transport of the hydrophobic monomer through the monomer droplets via the surfactant. The key to making a good pre-emulsion is to ensure that the monomer addition sequence is most hydrophobic first and most hydrophilic last. If this rule is not followed, the pre-emulsion is most likely to fail.

The pre-emulsion is prepared by adding the surfactant from group C with stirring. Group D was added to the mixture in the order EA, MMA and 3-methacryloxypropyltrimethoxysilane, GDMA, HPMA and MAA. The mixture was stirred for 5 minutes. Stability was checked by sampling and checking for phase separation by mixing at moderate speed. The mixture speed was increased to eliminate any phase separation. If phase separation occurs, the speed is increased to "stir up" the mixture.

66g C and D were then added to the flask at 77 ℃ and held for 5 minutes. Then group E was added at 77 ℃. The temperature was raised to 79.8 ℃ after the temperature passed the peak temperature. The remaining C and D were then pumped into the flask over 180 minutes. The pump was washed using F while it was being pumped into the flask. The batch was held at 80 ℃ for 15 minutes. Then G was added and held for 5 minutes. The reactor was then cooled to 70 ℃. H was added over 20 minutes and held at 70 ℃ for 15 minutes. I was then added over 30 minutes at 40 ℃. The batch was cooled to 38 ℃ and filtered.

Example 2

Example 1 was repeated with the following compounds. 0.5% by weight, based on the total weight of the monomers, of 3-Methacryloxypropyltrimethoxysilane (MPS) was added to group D.

Example 3

Example 1 was repeated with the following compounds. 1.1% by weight, based on the total weight of the monomers, of 3-Methacryloxypropyltrimethoxysilane (MPS) were added to group D.

Example 4

Example 1 was repeated with the following compounds, except that no GDMA was present. 1.1% by weight, based on the total weight of the monomers, of 3-Methacryloxypropyltrimethoxysilane (MPS) were added to group D.

Example 5

Example 1 was repeated with the following compounds, except that no GDMA was present. 2.0% by weight, based on the total weight of the monomers, of 3-Methacryloxypropyltrimethoxysilane (MPS) were added to group D.

Example 6

Example 1 was repeated with the following compounds without using the procedure of group I. 5.0% by weight, based on the total weight of the monomers, of 3-glycidoxypropyltrimethoxysilane (Dynasylan)) Add to group D.

Example 7 latex emulsion overview of examples 1-6

The latex emulsions of examples 1-6 were all prepared using an emulsion polymerization process. The properties are summarized in table 1.

TABLE 1 (latex emulsions of examples 1-6)

Example 1 has 6% of 1, 3-Glycerol Dimethacrylate (GDMA) which can crosslink the latex emulsion polymer. The gel content was about 50%. Example 2 has 6% 1, 3-Glycerol Dimethacrylate (GDMA) and 0.5% 3-Methacryloxypropyltrimethoxysilane (MPS). The gel content increased to 88%. Example 3 has 1.1% 3-Methacryloxypropyltrimethoxysilane (MPS) and 6% GDMA. The gel content of this example increased to 99.7%. Example 4 had 1.1% 3-Methacryloxypropyltrimethoxysilane (MPS) and no GDMA. The gel content was about 94%. Example 5 has 2.0% 3-Methacryloxypropyltrimethoxysilane (MPS) and no GDMA. The gel content was not increased compared to example 4. Example 6 with 5% 3-glycidoxypropyltrimethoxysilane (Dynasylan)) And 6% of 1.3-Glycerol Dimethacrylate (GDMA). The gel content was higher than in example 1 and lower than in examples 2-5.

The results show that 3-Methacryloxypropyltrimethoxysilane (MPS) is more effective in increasing the gel content of the particles. The higher gel content provides better blush and chemical resistance to the hybrid latex emulsion.

The crosslinking reaction depends on the MPS concentration. The greater the amount of MPS in the monomer feed, the higher the degree of condensation of the silica-based network (examples 2-4). However, when the MPS concentration is too high as in example 5, the degree of condensation may be reduced because MPS has bulky branched hydrophilic groups and stable alkylsilyl groups, which cannot be hydrolyzed and can prevent excessive crosslinking and coagulation of the monomers during emulsion polymerization.

Example 5 has a small amount of pellets in the reactor.

The particle size of all examples was small (<120 nm).

The results shown in table 1 relate to a sol-gel process for preparing highly mixed organic-inorganic hybrid latex emulsions. The silica particles can more effectively improve chemical and water resistance of the hybrid latex emulsion. Methacrylic silane monomers such as 3-methacryloxypropyltrimethoxysilane (0.5-2%) can be copolymerized with acrylate monomers to form interpenetrating network latex emulsions. The gel content of the mixed latex emulsion containing 1.1% of silane methacrylate increased from 50% to 99.7%. The water whitening resistance of the mixed latex emulsion is also improved.

Dynasylan Glymo is a bifunctional organosilane with a reactive epoxide and a hydrolysable inorganic methoxysilyl group. The epoxide may react with functional groups in the polymer chain, such as acid groups and hydroxyl groups. Hydrolysis of the methoxy groups of Dynasylan Glymo in the latex emulsion yields silanol groups, which can then condense with silanol groups on nanosilica to form siloxanes. However, the gel content of example 6 was lower than the MPS latex emulsion. A catalyst such as an amine may be required to promote the crosslinking reaction. Dynasylan Glyeo may also be used in emulsion polymerization.

EXAMPLE 8 preparation of coating composition

The 6 latex samples prepared in examples 1-6 were formulated with various additives such as solvents and waxes. The paint formulation is summarized as follows:

the coating composition was applied to a 211TFS substrate and baked at a metal peak temperature of 234 ℃ for 9 seconds. The coating weight range is about 2.0-2.7msi (milligrams per square inch). The test results are summarized in table 2 below. The coating films prepared from examples 3 and 4 exhibit excellent flexibility/adhesion, blush resistance and blistering resistance and have good cure response at short residence times on both aluminum and 211TFS substrates. The mixed latex emulsion with 3-Methacryloxypropyltrimethoxysilane (MPS) is more effective in improving the gel content of particles and the performance of coating films.

TABLE 2 coating composition Properties

Coating material	Whitening resistance(distilled immersion at 250 ℃ F. for 90 minutes)	Foaming	Adhesion	Beaded erichsen cup
					Example 1	3	Is dense	0	Without cracking or breaking
Example 2	2	Is dense	0	Without cracking or breaking
					Example 3	<1	Several of	0	Without cracking or breaking
Example 4	<1	Several of	0	Without cracking or breaking
					Example 5	2	Medium and high grade	0	Without cracking or breaking
Example 6	2	Medium and high grade	0	Without cracking or breaking

Claims

1. A coating composition comprising a hybrid latex emulsion prepared by a process comprising the steps of:

a) mixing an ethylenically unsaturated monomer component and a stabilizer in a carrier to form a monomer emulsion; and

b) reacting the monomer emulsion with an initiator to form the hybrid latex emulsion,

wherein the ethylenically unsaturated monomer component comprises an organosilane compound and at least one ethylenically unsaturated monomer that is not an organosilane compound,

wherein the coating composition has a gel content of greater than 50%,

wherein the organosilane compound is present in an amount of 0.1 to 30 weight percent based on total solids of the hybrid latex emulsion, and

wherein the organosilane compound comprises 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, vinyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, or a combination thereof.

2. A coating composition according to claim 1, wherein the organosilane compound comprises a reactive organic group and a hydrolysable inorganic alkoxysilane.

3. The coating composition of claim 1, wherein the stabilizer comprises dodecylbenzene sulfonic acid, dinonylnaphthalene disulfonic acid, di (2-ethylhexyl) sulfosuccinic acid, or a combination thereof.

4. The coating composition of claim 1, wherein the hybrid latex emulsion further comprises a crosslinker.

5. The coating composition of claim 1, wherein the ethylenically unsaturated monomer component comprises tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerol di (meth) acrylate, glycidyl methacrylate, 1, 4-butanediol di (meth) acrylate, hydroxypropyl (meth) acrylate, (meth) acrylic acid, vinyl monomers, acrylic monomers, allylic monomers, acrylamide monomers, vinyl esters, vinyl halides, vinyl aromatics, vinyl aliphatic hydrocarbon monomers, vinyl alkyl ethers, acrylic monomers, 1, 3-butanediol (meth) acrylate, polyalkylene glycol di (meth) acrylate, diallyl phthalate, vinyl esters, vinyl aromatic hydrocarbons, vinyl aliphatic hydrocarbon monomers, vinyl alkyl ethers, acrylic monomers, 1, 3-butanediol (meth) acrylate, polyalkylene glycol di (meth) acrylate, diallyl phthalate, vinyl esters, vinyl aromatic hydrocarbons, vinyl esters, Trimethylolpropane tri (meth) acrylate, divinylbenzene, divinyltoluene, trivinylbenzene, divinylnaphthalene, or a combination thereof.

6. The coating composition of claim 1, wherein the hybrid latex emulsion is formed using a crosslinker comprising a phenolic resin, a urea-formaldehyde resin, a phenol-formaldehyde resin, a benzoguanamine-formaldehyde resin, or a combination thereof.

7. A method of coating a substrate comprising applying a coating composition according to claim 1 to the substrate.

8. The method of claim 7, wherein the substrate is a lid of a beer or beverage container.

9. A substrate coated with the coating composition of claim 1.